SN65ELT21 Questions

Richard Elmquist

Other Parts Discussed in Thread: SN65ELT21

I have looked at the data sheet for the SN65ELT21 and the (+) and (-) inputs seem to be rated up to 6V. There does not appear to be any protection diodes present as there is no clamp current specified.

The customer is seeing the following:

Currently in our design we have 2 power supplies that can come up in different orders. One of the supplies is used to power a PECL driver and the other is used to power the SN65ELT21 PECL receiver. We are seeing that when the driver is powered and the Receiver is not that there is voltage coupling across the SN65ELT21 chip. I have measured 1.8 V at the VCC pin on SN65ELT21. We previously used the On-Semi MC100ELT21 and don’t see this behavior on those prototype modules. Is this expected behavior??

Is this something that the customer should be seeing? Are there clamp diodes present on the inputs that are not specified? Can you explain how the customer is seeing a voltage at Vcc with no Vcc present? Does this simply mean that the chip is damaged?

Thanks for your help with this!

Richard Elmquist

over 7 years ago

0 Richard Elmquist over 7 years ago

TI__Mastermind 45250 points

Has anyone had a chance to look at the request above?

Can you give a time frame as to when you might be able to provide the information?

Thanks for your help with this!

Richard Elmquist

0 Diego Cortes over 7 years ago in reply to Richard Elmquist

TI__Mastermind 36085 points

Hello,

There is a dual-diode ESD protection on these inputs, so that would explain why there is a voltage at VCC with no VCC present.

Regards,

Diego.

0 Richard Elmquist over 7 years ago in reply to Diego Cortes

TI__Mastermind 45250 points

Diego,

Thanks for your response!

I will let you know if the customer has any additional questions.

Thanks again.

Richard Elmquist

0 Richard Elmquist over 7 years ago in reply to Richard Elmquist

TI__Mastermind 45250 points

Diego,

If this situation happens in their application will it cause damage to the part in any fashion?

Can it latch up?

Or will the part operate normally once the proper Vcc level is applied to the IC?

Thanks for your help with this!

Richard Elmquist

0 Richard Elmquist over 7 years ago in reply to Richard Elmquist

TI__Mastermind 45250 points

Diego,

Did you get a chance to look at the questions I posed in the previous email?

Thanks for your help with this!

Richard Elmquist

0 Diego Cortes over 7 years ago in reply to Richard Elmquist

TI__Mastermind 36085 points

RIchard,

The device shall work normally once VCC is present, I 'don't have the part to run a test and verify that the SN65ELT21 is not operating when VCC is off, so please suggest to disregard any output data when VCC is off (if there is any).

Regards,

Diego.

0 Richard Elmquist over 7 years ago in reply to Diego Cortes

TI__Mastermind 45250 points

Diego,

Thanks for your help!

I will let you know if the customer has any further questions.

Thanks again.

Richard Elmquist

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SN65ELT21 Questions